考虑水泥土桩劣化的复合地基设计理论与关键技术研究

发布时间：2018-05-12 04:02

本文选题：水泥土桩 + 劣化　；参考：《山东大学》2015年硕士论文

【摘要】：在道路建设中,水泥土搅拌桩是软弱地基加固的一种常用方法,利用专用设备将粉状或浆状水泥与地基土原位搅拌形成粉喷桩或浆喷桩复合地基。另外,《公路路基设计规范(JTG D30-2004)》规定：对滨海路堤,当路堤两侧有较大的水头差时,可在路堤中心设置防渗墙(厚度一般为300-400mm)进行防渗加固。然而,在滨海和一些内陆地区,如吹填造陆区,地下水的矿化度很高,甚至是矿化度大于50g·L-1的卤水,这将导致水泥土性能劣化。但是,目前相关道路规范中均未考虑水泥土的劣化效应,虽然《建筑地基基础设计规范(JGJ79-2011)》中规定：水泥土搅拌法用于地下水具有腐蚀性地区时,必须通过现场试验确定其运用性。但是,如何确定其运用性,规范中没有给出具体的确定方法。因此目前缺乏含盐地下水地区水泥土桩全寿命周期承载能力预测方法,以及水泥土桩劣化对复合地基沉降的影响规律研究。本文以黄河三角洲粉土地基为例,围绕滨海水泥土桩劣化效应这一关键科学问题开展研究。在对黄河三角洲典型区域地下水质和土力学性质进行调查和分析基础上,利用试验、理论和数值分析等综合手段,对水泥土桩复合地基设计理论与关键技术进行了研究：以黄河三角洲滨德高速盐水环境下水泥土搅拌桩为例,研究腐蚀性地区水泥土劣化情况复合地基的长期承载力,提出了一种预测腐蚀性地区水泥土长期承载力的方法,并将提出公式的计算结果与其他人的研究结果进行了比对,发现公式的预测性能良好；以黄河三角洲东营港滨海公路复合地基为例,通过数值模拟计算方法研究不同桩径水泥土桩的劣化对水泥土复合地基沉降规律的影响,研究发现桩径越大沉降越小,且水泥土桩的劣化主要对水泥土桩加固区的沉降影响较大,对下卧层的影响较小,对路基中间部分影响较大,边缘部分较小；基于达西定律,以中国青岛胶州湾海相吹填土为例,研究了水泥土劣化层渗透系数的早期演化规律,发现劣化深度的发展随龄期的增大显现出增加速率逐渐减小的趋势,且水泥土劣化层的渗透性随龄期的增大而增大。
[Abstract]:In road construction, cement-soil mixing pile is a common method for strengthening soft foundation. Cement or slurry cement is mixed with foundation soil in situ to form powder jet pile or grouting pile composite foundation with special equipment. In addition, JTG D30-2004 > provides that when there is a large water head difference on both sides of the embankment, the impervious wall (300-400mm in thickness) can be installed in the center of the embankment. However, in coastal and inland areas, such as reclaimed land areas, the salinity of groundwater is very high, even brine with salinity greater than 50 g L-1, which will result in the deterioration of cement-soil performance. However, the deterioration effect of cement soil is not considered in the relevant road codes at present, although it is stipulated in the Code for Design of Building Foundation (JGJ79-2011) that when cement soil mixing method is used in corrosive areas of groundwater, Its applicability must be determined by field tests. However, how to determine its applicability, the specification does not give a specific determination method. Therefore, there is a lack of prediction method for the life-cycle bearing capacity of cement-soil piles in saline groundwater area and the study on the influence of the deterioration of cement-soil piles on the settlement of composite foundation. Taking the silt foundation in the Yellow River Delta as an example, this paper focuses on the key scientific problem of the degradation effect of cement soil piles in coastal areas. On the basis of investigation and analysis of underground water quality and soil mechanics properties in typical regions of the Yellow River Delta, comprehensive means such as test, theory and numerical analysis are used. The design theory and key technology of cement-soil pile composite foundation are studied. The long-term bearing capacity of cement soil degradation composite foundation in corrosive area is studied by taking cement-soil mixing pile in high-speed brine environment of Yellow River Delta as an example. A method of predicting long-term bearing capacity of cement soil in corrosive area is put forward, and the calculation results of the formula are compared with the results of other people's research, and it is found that the prediction performance of the formula is good. Taking the composite foundation of Dongying Port Binhai Highway in the Yellow River Delta as an example, the influence of the deterioration of different pile diameter on the settlement of cement-soil composite foundation is studied by numerical simulation method. It is found that the bigger the diameter of pile is, the smaller the settlement is. The deterioration of cement-soil pile has a great influence on the settlement of cement-soil pile reinforcement area, a small influence on the subgrade, a greater influence on the middle part of the roadbed, and a smaller edge part; based on Darcy's law, the degradation of the cement-soil pile has a great effect on the settlement of the cement-soil pile. The early evolution law of permeability coefficient of cement soil degradation layer is studied with the example of marine blowing fill in Jiaozhou Bay, Qingdao, China. It is found that the development of deterioration depth shows a decreasing trend with the increase of age. And the permeability of cement soil increases with the increase of age.
【学位授予单位】：山东大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：U416.1

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